1. Field of the Invention
The present invention relates to a substrate for a liquid-ejection head, a liquid ejection head, a method for manufacturing a substrate for a liquid-ejection head, and a method for manufacturing a liquid ejection head.
2. Description of the Related Art
As a recording device that performs recording operation by ejecting liquid, an ink jet printer that ejects ink is widely known. A liquid ejection head for use in such a recording device is provided with a substrate for a liquid-ejection head having an energy generating element that generates energy in order to eject liquid and a flow path member constituting a part of an ejection port or a liquid flow path. The substrate for a liquid-ejection head is provided with a supply port that supplies liquid to the energy generating element in such a manner as to penetrate a silicon base.
In recent years, in order to increase the color developability and durability of recorded images, the use of a strong alkaline liquid for ink has been examined. Since silicon dissolves in an alkaline solution, there is concern whether the silicon on the wall surface of the supply port dissolves in ink. In order to deal with the concern, U.S. Pat. No. 7,517,059 discloses a structure such that a protection layer is provided on the inner wall of the supply port so that the inner wall of the supply port does not dissolve in liquid.
In contrast, silicon compounds, such as silicon oxides and nitrides, are frequently used for an insulating layer that protects the energy generating element and is provided at the position facing the flow path, so that the energy generating element and line connected thereto are electrically insulated from ink.
However, as disclosed in U.S. Pat. No. 7,517,059, the protection performance of the insulating layer gradually decreases simply by forming a protection layer 15 at the inner side of the supply port, depending on the type and the use state of ink. Or, there is concern that ink leaks to line from a gap between the protection layer of the supply port and the insulating layer.